My son had a thinning of the aortic root.And its gone. Is it possible?

My son had a thinning of the aortic root . Now four years later a different hospital did a 2d echo and they? said its gone how can that be?? Is it a miracle? cause thoughs defects get worse as you grow not better. Ten years ago a speacialist saw it many times I dont understand. I m glad and I hope its true cause he could not play sports for along time now hes doing everything. What could have happened??? Does anyone know anything about this kind of problem?????